Strain gage pressure sensor wherein a gap is maintained between the diaphragm and the substrate

Abstract

A pressure sensor prevents the occurrence of a large deformation or breakage of the diaphragm in a strain gage-type pressure sensor utilizing a thin plate-shaped insulating body as the diaphragm. The pressure sensor comprises an insulating diaphragm having a strain gage on its surface and a substrate positioned opposing the surface of the diaphragm on which the strain gage is mounted and kept a predetermined distance away from the surface. The diaphragm can be formed of material such as ceramic of alumina, zirconia or the like, silicon or crystal. The substrate can be formed of either the same material as the diaphragm, or the surface opposing the diaphragm can be formed of an insulator disposed on metal. The diaphragm and the substrate can be affixed using a low-melting glass.

We claim: 
     
       1. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   said gap is predetermined such that the substrate limits deformation of said diaphragm; and   an insulating body formed of at least one of ceramic, silicon and crystal is used as the diaphragm.   
     
     
       2. The pressure sensor of claim 1 wherein said substrate is formed of the same material as said diaphragm. 
     
     
       3. The pressure sensor of claim 1 wherein said diaphragm and said substrate are fixed using a fixing medium. 
     
     
       4. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm; and   said diaphragm and said substrate are fixed using a fixing medium.   
     
     
       5. The pressure sensor of claim 1 wherein: said diaphragm and said substrate are fixed using a fixing medium; and   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin.   
     
     
       6. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm;   said diaphragm and said substrate are fixed using a fixing medium; and   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin.   
     
     
       7. The pressure sensor of claim 1 wherein: said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin; and   a gap forming member having a predetermined diameter is included in said adhesive.   
     
     
       8. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm;   said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin; and   a gap forming member having a predetermined diameter is included in said adhesive.   
     
     
       9. The pressure sensor of claim 1 wherein said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm. 
     
     
       10. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       11. The pressure sensor of claim 1 wherein: said diaphragm and said substrate are fixed using a fixing medium; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       12. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm;   said diaphragm and said substrate are fixed using a fixing medium; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       13. The pressure sensor of claim 1 wherein: said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       14. The pressure sensor of claim 1 wherein: said substrate is formed of the same material as said diaphragm;   said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes an adhesive comprising at least one of a low-melting glass and a thermosetting resin; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       15. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   said gap is predetermined such that the substrate limits deformation of said diaphragm; and   an electric circuit wiring pattern is formed on the surface of said substrate.   
     
     
       16. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   said gap is predetermined such that the substrate limits deformation of said diaphragm; and   a circuit board having an electric circuit wiring pattern is adhered to the surface of said substrate.   
     
     
       17. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   an electric circuit is placed on the surface of said substrate, and said pressure sensor is fixed inside a container through an elastic member.   
     
     
       18. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   an insulating body formed of at least one of ceramic, silicon and crystal is used as the diaphragm; and   a return portion of a resistor for the strain gage formed on said substrate has no angle.   
     
     
       19. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   an insulating body formed of at least one of ceramic, silicon and crystal is used as the diaphragm; and   the resistance value of a return portion of a resistor for the strain gage formed on said diaphragm is reduced relative to another portion of the resistor.   
     
     
       20. The pressure sensor of claim 19 wherein the resistance value of the return portion of the resistor for the strain gage formed on said substrate is reduced by forming the return portion by a low resistance material. 
     
     
       21. The pressure sensor of claim 19 wherein the resistance value of the return portion of the resistor for the strain gage formed on said diaphragm is reduced by widening the width of said return portion. 
     
     
       22. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   an insulating body formed of at least one of ceramic, silicon and crystal is used as the diaphragm; and   a resistor for the strain gage mounted on said diaphragm is formed by printing.   
     
     
       23. The pressure sensor of claim 22 wherein at least one of a silver-palladium alloy paste material and a ruthenium tetroxide paste material is printed and baked to form said resistor. 
     
     
       24. A pressure sensor comprising: an insulating diaphragm having a strain gage mounted on a surface thereof; and   a substrate positioned opposing the surface of said diaphragm on which the strain gage is mounted, said substrate positioned so as to maintain a gap between said surface of the diaphragm on which the strain gage is mounted and said substrate; wherein   said gap is predetermined such that the substrate limits deformation of said diaphragm; and   an insulating body formed of at least one of ceramic, silicon and crystal is used as the diaphragm; and   a surface of a resistor for the strain gage mounted on said diaphragm is covered with a protective material.   
     
     
       25. The pressure sensor of claim 24 wherein a glass having higher melting point than the baking temperature of a sealing member is utilized as said protective material. 
     
     
       26. The pressure sensor of claim 1 wherein the ceramic of the insulating body is at least one of alumina and zirconia. 
     
     
       27. The pressure sensor of claim 1 wherein the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal. 
     
     
       28. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal; and   said diaphragm and said substrate are fixed using a fixing medium.   
     
     
       29. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal;   said diaphragm and said substrate are fixed using a fixing medium; and   said fixing medium includes at least one of an adhesive comprising a low-melting glass and a thermosetting resin.   
     
     
       30. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal;   said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes at least one of an adhesive comprising a low-melting glass and a thermosetting resin; and   a gap forming member having a predetermined diameter is included in said adhesive.   
     
     
       31. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       32. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal;   said diaphragm and said substrate are fixed using a fixing medium; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.   
     
     
       33. The pressure sensor of claim 1 wherein: the surface of said substrate opposing the diaphragm is formed of an insulator disposed on metal;   said diaphragm and said substrate are fixed using a fixing medium;   said fixing medium includes at least one of an adhesive comprising a low-melting glass and a thermosetting resin; and   said gap is formed by forming a concave on the surface of said substrate opposing said diaphragm.